The stipules of Comptonia peregrina

Abstract

The serial changes in stipule expression were examined in C. peregrina (L.) Coult. for the various categories of appendages on a branch, i.e., prophylls, remaining bud scales, foliage leaves and the distal cluster of scalelike leaves. Stipules are not associated with the 2 prophylls and they are not evident on the remaining 2 bud scales at maturity. Stiples are initiated on the leaf base on these 2 bud scales and are raised up on the free leaf base, which constitutes the protective scale. Approximately 18 stipulate foliage leaves form. Their stipules arise on the leaf base and assume a cauline position at maturity. The foliage leaf has no free leaf base. Numerous lanceolate leaves with basally connate, lanceolate stipules, scale leaves with stipule lobes and scale leaves without stipule lobes form sequentially on the distal portion of the branch which eventually aborts and abscises. Most of the scale leaf is free leaf base. Correlations may be drawn between distal scale leaf and bud scale development (proportion of free leaf base to upper leaf zone, lack of internode expansion and small dimensions of the shoot apex at the time of inception of these structures). Prophylls are considered to be unique structures because of their position, precocious inception, leaf base-stem relationship, lack of stipules and single vascular bundles. The phylogeny of stipules is unknown but in view of the proposed origin of the megaphyllous leaf the question is asked whether stipules may be considered homologous to prophylls.